Updated: 02 July 2005
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   pammixinterlace  -  mix adjacent lines to merge interlaced im-


   pammixinterlace [infile]


   This program is part of Netpbm.

   pammixinterlace is meant to operate on an image which  is  the
interlacing of
   two images, where raster rows 0, 2, 4, etc. are from one image
and rows 1,
   3,  5,  etc.  are from another. (See below for why  you  might
expect to
   encounter such an image).

   pammixinterlace  makes each row of the output a mixture of the
   row of the input and its two neighbors. It uses  half  of  the
main row and a
   quarter each of the two neighbor rows.

   This can be useful if the image is a video capture from an in-
terlaced video
   source. In that case, each row shows the subject  1/60  second
before or after
   the  two rows that surround it. If the subject is moving, this
can detract
   from the quality of the image.

   In video data streams, you often find each frame contains only
half the rows
   of  the  image -- the odd half or the even half. The displayer
of the stream
   displays the rows in their proper positions on a CRT  as  they
come in. When
   you  display  the rows in this order, the CRT has less flicker
because a
   particular area of the screen gets refreshed twice  as  often.
In the process
   of  capturing  such a stream, computers often generate the in-
terlaced image of
   the type that pammixinterlace works with. But this  interlaced
image, when
   displayed  on  a CRT, does not look the same as if a displayer
were rendering
   the stream directly on a CRT as it  arrived,  because  of  the
timing of when
   the various pixels get drawn and subsequently fade. That’s why
you need
   something like pammixinterlace.

   You may prefer the effect of simply extracting one of two  im-
ages. You can do
   that with pamdeinterlace.


   pamdeinterlace, pam pnm

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